The present invention generally relates to a device and method for the in situ sampling of breath air at a predetermined minimum flow of breath air and, in particular, relates to such a device including a heatable housing having a mouthpiece, a directional control valve the inlet of which is connected to the mouthpiece, at least one needle connected to a first outlet of the directional control valve and an air-tightly closed sample vessel adapted to be pushed on the needle.
In general, methods for examining the breath air for alcohol are known, for example, (Drager issue 322, 1982; Drager-company brochure Alkcotest 7010, 1981). Therein, a minimum flow of breath air is conducted through a measuring instrument during a predetermined time interval. The measuring instrument includes a semiconductor sensor responding to alcohol or measures the alcohol absorption in the range of 3-4 .mu.m. Therein, the condensation of humidity from the breath air is prevented by heating devices.
In another publication of N. Bilzer, M. Kramer, O. Gruner "A Method for the Determining of Poreath Alcohol with Multifract (Gaschromatography)" in "Proceedings Int. Conference for Alcohol, Drugs and Traffic Safety" 1980 vol. 2 page 691, publisher Almquist+Wikselt Int., Stockholm; a device for sampling breath air is described. The device is mounted in a heatable housing provided with a mouthpiece. The mouthpiece is connectable to the atmosphere and to a collecting chamber, respectively, via a two-way directional control valve. In the collecting chamber a piston is movable under the pressure of the breath air into a predetermined end position for accommodating a measured sample volume. The outlet of the collecting chamber is connected through a needle to an air-tightly closed sample vessel adapted to be attached to this needle, and through another two-way directional control valve closed during the sampling to a nitrogen source for the purpose of rinsing. The sample vessel is closed by a self-sealing membrane adapted to be pierced and is evacuated to accommodate the sample.
In another method the breath air is conducted directly through a measuring instrument which is matched for the particular application and the measurement is made in the air flow. It is, however, inappropriate to operate with a measuring instrument responding specifically to one component when the composition of the breath air at a working place has to be examined and qualitatively and quantitatively analysed for different components, which result, for example, from the metabolism of inhaled vapors. Therefore, it is more appropriate to take a sample of the breath air at the working place and to examine the breath air at another place.
The device described in the publication mentioned in the beginning is a laboratory instrument, which requires an evacuated sample vessel to be used. This device cannot be used at the work place itself.